The commercial planning is concentrated on medium-term decisions and the focus of this level in maritime fleet operation is primarily on optimal routing and scheduling. In industrial shipping the cargo owner or shipper normally controls the ships’ operations. Industrial operators try to ship all their cargoes at minimum cost. A tramp shipping company, on the other hand, may have a certain amount of contract cargoes that it is committed to carry and tries to maximize the profit from optional cargoes. During the last decades, there has been a shift from industrial to tramp shipping. Perhaps the main reason is that many cargo owners are now focusing on their core business and have outsourced other activities like transportation to independent shipping companies. From the shipper’s perspective, this outsourcing has resulted in reduced risk.
Liner shipping differs significantly from the other two types of shipping operations, i.e. tramp and industrial. However, the liner shipping involves significant commercial decisions at different planning levels. The differences among the types of shipping operations are also manifested when it comes to routing and scheduling issues. One main issue for liners on the commercial planning level is the assignment of vessels to established routes or lines; this is referred to as “fleet deployment”.
A focus on a fleet deployment problem where the shipping company utilize the different cruising speeds of the ships in the fleet is important. The routes are pre-defined, and each route will be sailed by one or more ships several times during the planning period. Each route has a defined common starting and ending port. A round-trip along the route from the starting port is called a voyage.
The demand is given as a required number of voyages on each route without any explicit reference to the quantities shipped. The fleet of ships is heterogeneous and it can be assumed that not all ships can sail all routes. Such a specification can incorporate needed ship capacity together with compatibilities between ships and ports. With information about the feasible ship-route combinations and the company’s fleet mix, the relevant decisions on fleet deployment are taken. Of course, minimization of cost and maximization of profits is one main factor; however and in particular for liner operators, minimization of fuel cost and thus reduction of fleet CO2 emissions becomes an important decision making aspect at this level (MariEMS 2017).